Assisting FGL oscillations with perpendicular anisotropy for MAMR

A spin transfer oscillator (STO) structure, comprising:

• (a) a seed layer formed on a substrate;
• (b) a spin injection layer (SIL) having perpendicular magnetic anisotropy (PMA);
• (c) a field generation layer (FGL) having top and bottom surfaces and with a magnetic moment in an in-plane direction;
• (d) a first PMA assist layer that adjoins one of the top and bottom surfaces of the FGL layer and is separated from the SIL by a first spacer;
• and
• (e) a second PMA assist layer that is separated from the other of the top and bottom FGL surfaces by a second spacer, said second PMA assist layer has a synthetic structure comprised of a first PMA layer with a first thickness, a second PMA layer with a second thickness less than the first thickness, and a coupling layer formed between the first and second PMA layers wherein all of the aforementioned layers including the seed layer, SIL, FGL, first and second PMA assist layers, and first and second spacers are formed in a stack on the substrate.

A method of forming a STO structure, comprising:

• (a) depositing a composite seed layer on a substrate, said composite seed layer has a Ta/M1 or Ta/M1/M2 configuration wherein the M1 layer is a metal with a fcc(111) or hcp(001) crystal orientation, and M2 is a metal unequal to M1;
• (b) forming a stack of layers on the composite seed layer, comprising:
• (1) a spin injection layer (SIL) having perpendicular magnetic anisotropy (PMA);
• (2) a composite field generation layer (FGL) having a synthetic anti-ferromagnetic (SyAF) configuration wherein a first FGL layer with a first thickness and a second FGL layer with a second thickness that is less than the first thickness have magnetic moments in opposite in-plane directions and are separated by a coupling layer;
• (3) a first PMA assist layer that adjoins a surface of the first FGL layer and is separated from the SIL by a first spacer;
• (4) a second PMA assist layer that is separated from the second FGL by a second spacer;
• and
• (5) a capping layer;
• and
• (c) annealing said seed layer, capping layer, and said stack of layers.

A method of forming a STO structure, comprising:

• (a) depositing a composite seed layer on a substrate, said composite seed layer has a Ta/M1 or Ta/M1/M2 configuration wherein the M1 layer is a metal with a fcc(111) or hcp(001) crystal orientation, and M2 is a metal unequal to M1;
• (b) forming a stack of layers on the composite seed layer, comprising:
• (1) a spin injection layer (SIL) having perpendicular magnetic anisotropy (PMA);
• (2) a field generation layer (FGL) with a magnetic moment in an in-plane direction, and having top and bottom surfaces;
• (3) a first PMA assist layer that adjoins one of the top and bottom surfaces of the FGL and is separated from the SIL by a first spacer;
• (4) a second PMA assist layer that is separated from the other of the top and bottom FGL surfaces by a second spacer, said second PMA assist layer has a synthetic structure comprised of a first PMA layer with a first thickness, a second PMA layer with a second thickness less than the first thickness, and a coupling layer formed between the first and second PMA layers;
• and
• (5) a capping layer;
• and
• (c) annealing said seed layer, capping layer, and said stack of layers.